Dynamometer Test Results For The Surbo

In the Surbo research car, the Peugeot 405 1.6, the Surbo was dynamometer tested to prove that it gave more torque and power than the same car with no Surbo. The front wheels were removed and the dyno testers fixed in their place. 4th gear was used and the engine was run at steady speed before it was pushed to the rpm limit in 8 seconds each time. The closely-spaced time stamps show that the car was first tested with two surbos, then one surbo and finally no surbo. This removes any long-term effects, or changes in engine condition due to servicing or modifications.
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The graph above shows increased torque and power over the whole rpm range (thick line=Surbo, dotted {faint} line no Surbo). The torque increased by 108/93 Nm, or 16%, and is more accessible as it peaked at 3300 rpm instead of 4300 rpm originally. Power was up by 69.4/65=6.7% at the maximum.

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The Twin Surbo (thick line) was even more torquey, as its torque peaked at an even lower 2850 rpm (103.5/87.7=18% more at this common cruising speed). This makes driving or overtaking feel good on the highway.

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This graph shows that the Twin Surbo was stronger in torque from 2450 rpm to 3150 rpm. Therefore for those who do not rev much, or who cruise* in 5th gear between 90 kph and 115 kph, the Twin Surbo will help them save more fuel. For super highways where speeds exceed 115 kph (such as the Malaysian highway), the single Surbo will save more fuel due to greater torque. This also means that the single Surbo is better for revving between 3150 rpm and 4900. The Twin Surbo's power peaked at 5100 rpm, earlier than the single Surbo, and this may mean different tops speeds depending on the gearing.
*Gearing (5th of this car): 110 kph at 3000 rpm, or 36.67 kph/1000 rpm, or 22.63 mph/1000 rpm.

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This is the time graph comparison between the single Surbo and the Twin Surbo. The Twin Surbo (faint line) had more torque than the single Surbo (thick line) from 1.5 seconds to 2.7 seconds. The single Surbo led from the 3rd to close to the 6th second. The Twin Surbo reached its peak power of 69.2 HP in 6 seconds but the single Surbo took 8 seconds to hit its maximum of 69.4 HP. This may explain why the Twin Surbo is often faster for 0-100 kph times. The difference at other speeds must be done by road testing.

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Power is maximised when the Surbo is activated (as far as possible like in How It Works). The peak power was 71.65/65=10% more this way.